Xylan is one of the ubiquitous, naturally occurring polysaccharides, and is a major constituent of plants. From a structural viewpoint, xylan is a macromolecular polysaccharide containing a main chain made from units of xylose, which is polymerized by β-1,4 xyloside linkage. Xylan is present in nature not only as a homoxylan consisting of only xylose, but also as a heteroxylan such as arabinoxylan containing branched arabinose attached to the main chain.
Xylanase is a generic term for a group of enzymes that hydrolyze xylan, and that are widely found in animals, plants, and microorganisms. There has been research largely focusing on xylanase derived from bacteria, actinomycetes, yeast, fungi, and the like. Xylanase is used in production of xylooligosaccharides or xylose from xylan, as well as in biomass processing. In particular, xylanase has recently been brought to attention as being useful from the point of view of enzyme utilization in biomass processing. For example, xylanase is used in enzymatic degradation of agricultural waste for alcohol fuels, enzymatic treatment for liberating saccharides in animal feed, enzymatic treatment for dissolving pulp in the step of obtaining cellulose, and enzymatic treatment for bleaching wood pulp.
In the paper and pulp industry, recent years have seen increasing promise of using xylanase for improvement in whiteness and quality of pulp, reduction in the amount of chemical bleaching agents, such as chlorine bleaching agents, used in the pulp-bleaching step, and increase in pulp freeness in the paper-recycling step. Xylanase is also used in animal feed and in the food-processing field (Patent Document 1).
An object of the present invention is to provide a novel highly-active xylanase that is useful for applications, for example, in biomass decomposition, food processing, pulp bleaching, animal feed, and silage.